Carbonylation of olefins under mild conditions with minimum by-product formation based on palladium complex salts as catalysts, examples of which include palladium catalysts containing phosphines, phosphites, ammonia, amines, nitriles, and unsaturated hydrocarbons as ligands, is known.
Tsuji, Accounts Chem. Res. 2, 144-152 (1969) reviews palladium catalyzed carbon-carbon bond formation, including such carbonylation reactions. Bittler, et al., Agnew. Chem. Internat. Edit., 7, 329-335 (1968) disclose carbonylation of olefins under mild conditions in the presence of complex palladium (II) compounds and observe the Pd(O) compounds are inactive in the absence of added hydrogen chloride.
Several references disclose that certain metal halides, when added to the reaction mixture, improve the yield of linear products relative to branched products. These include, e.g., Mrowca, U.S. Pat. No. 4,257,973; Mrowca, U.S. Pat. No. 3,859,319; Butter, U.S. Pat. No. 3,700,706; Knifton, U.S. Pat. No. 3,919,272; and Knifton, J. Org. Chem., 41, 2885-2890 (1976). Use of such halides may pose corrosion problems. Fenton, U.S. Pat. No. 3,641,074 discloses the use of hydrogen and/or limiting mineral acid content of the reaction medium to favor the formation of linear rather than branched products.
Kajimoto, et al., U.S. Pat. No. 3,723,486 disclose the use of a palladium complex containing dichlorobenzene.
Yamaguchi, et al., U.S. Pat. No. 3,839,378 disclose the use of a palladium complex containing iodine or bromine and the use of hydrogen gas.
Cavinato et al., J. Mol. Catalysis, 10, 161-170 (1981), discuss effects of solvents on the hydrocarboalkoxylation of propylene with a palladium complex catalyst.
Hara, U.S. Pat. No. 3,793,369 discloses that it is desirable to employ a palladium complex with an aromatic tertiary phosphine, the molar ratio of the phosphine to palladium being 4:1 to 20:1.
von Kutepow, et al., U.S. Pat. No. 3,501,518, disclose carbonylation of olefins in the presence of metallic palladium or a palladium chalcogenide, a strong or medium strength acid (dissociation constant K&gt;10.sup.-4) and an organic phosphine or nitrile. Sulfuric acid, perchloric acid, phosphoric acid and hydrogen halides are disclosed as useful acids. von Kutepow, et al., U.S. Pat. No. 3,437,676 disclose carbonylation of olefins in the presence of a complex palladium salt, e.g., bis(triphenylphosphine) palladium dichloride. The reaction may be carried out in the presence of an organic or inorganic acid such as sulfuric acid, phosphoric acid, boric acid, acetic acid, propionic acid, other carboxylic acids and hydrogen halides.
It is also known that carbonylation of olefins can proceed in the absence of a metal catalyst if a high concentration of a strong acid is employed. For example, Booth, et al., J. Chem. Soc. Perkin I. 2441-2446 (1979) and Norrell, U.S. Pat. No. 3,965,132 disclose improved yields when trifluoromethanesulfonic acid is employed instead of sulfuric acid.
It is an object of this invention to provide a process for carbonylation of olefins which process does not employ corrosive halides and which provides an increase in reaction rate in comparison with that achieved using known strong acids such as sulfuric acid.